[Dynamics of Proliferation and Differentiation after Transplantation of Hematopoietic Cells in Mouse]

To observe the dynamic changes of hematopoietic reconstitution and multiple lineages differentiation at early phase after transplantation.

Whole bone marrow mononuclear cells (wBMMNC, 5×10⁶) and enriched c-Kit⁺ hematopoietic stem/progenitor cells (HSPC, 3×10⁵) from the BM of B6-Ly5.1 mice were transplanted into lethally irradiated B6-Ly5.2 mice, the frequencies and absolute numbers of donor-derived cells (including LKS^- and LKS⁺) were detected by flow cytometry. The multiple lineages differentiation of donor-derived cells was also monitored by flow cytometry. The homing and early phase proliferations of donor-derived cells were observed by two-photon microscope.

The donor-derived cells started to proliferation from 5-7 days after transplantation and reached the peak value at 2-3 weeks after wBMMNC transplantation. The donor-derived cells proliferated from 1-2 weeks and maintained until 4 weeks after c-kit⁺HSPC transplantation. At 1 week after transplantation, the donor-derived cells mainly differentiated into myeloid cells with a few lymphoid cells production (B cells) but the production of T cells was not observed at most in wBMMNC transplanted group, while myeloid cells occupied the majority of donor-derived cells at 2-4 weeks; donor-derived cells almost totally differentiated into myeloid cells at 1-3 weeks after transplantation in c-Kit⁺ transplanted group and donor-derived B cells appeared at 4 weeks. The absolute number of donor-derived LKS^- and LKS⁺ cells in the BM of c-Kit⁺ transplanted group were much higher than that of wBMMNC group (P＜0.001) at 2 weeks respectively. The clustering proliferation of cKit⁺ cells at 4-5 days after transplantation was observed by two photon microscope.

The dynamical rate of proliferation and reconstitution of donor-derived cells are much earlier and quicker in c-Kit⁺ group than those of wBMMNC group. c-Kit⁺ cells mainly differentiate into myeloid cells within 1-3 weeks and the lymphoid cell differentiation starts at 4 weeks after transplantation. The immediate proliferation and differentiation of c-Kit⁺ cells within 1 week maybe due to the urgent needs of hematopoietic regeneration under the myeloablated hosts.